Other Parts Discussed in Thread: LM324-N, LM324, LM2902KAV, LM2902K, LM324K, LM2902
I have an old PCB that I am updating so that it will pass the 15kV air discharge test. It is using the LM324N, and LM324AN interchangeably as voltage follower. After protecting the output lines with Zeners, everything was going great. Both -15kV and +15kV hits were dissipated correctly.
However a new batch of boards arrived and they started failing what appeared to be randomly. The difference was the LM324s. Every board that fails has the LM324AN, and the passing ones are using the LM324N. The difference from the datasheet is below. I am wondering if the Bias Current rating may be the reason for what appears to be better ESD protection?
I am guessing that output is not able to track the change to the input during the ESD event. Which may be reverse biasing one of the transistors internally, and in the case of the LM324A it’s too much to handle. Any insight into what may be going on would be greatly appreciated!
Supply +24V, input signal ~6.2V
|
LM324-N |
LM324A |
Unit |
||
|
TYP |
MAX |
TYP |
MAX |
|
Input Offset Voltage |
2 |
7 |
2 |
3 |
mV |
Input Bias Current |
45 |
250 |
45 |
100 |
nA |
Input Offset Current |
5 |
50 |
5 |
30 |
nA |